The use of herbicides to control undesirable vegetation such as weeds in crop fields has become almost a universal practice. The herbicide market exceeds 15 billion dollars annually. Despite this extensive use, weed control remains a significant and costly problem for farmers.
For example, present herbicides often impose special limitations on farming practices, and the time and method of application and stage of weed plant development often are critical for good weed control with such herbicides, thus creating farm management constraints. Furthermore, since only a few target enzymes are inhibited by currently used herbicides, various weed species are, or may become, resistant to these herbicides. For all of these reasons, the discovery and development of effective new herbicides, in particular those acting on novel target enzymes, is increasingly important.
Novel herbicides can now be discovered using high-throughput screens that implement recombinant DNA technology. Once identified, metabolic enzymes essential to plant growth and development can be recombinantly produced through standard molecular biological techniques and utilized as herbicide targets in screens for novel inhibitors of the enzyme's activity. The novel inhibitors discovered through such screens may then be used as herbicides to control undesirable vegetation. Such herbicides are also useful for selecting herbicide tolerant plants, and seed plants tolerant to the herbicide can be produced, for example by genetic engineering techniques. Thus, herbicides that exhibit greater potency, broader weed spectrum, and more rapid degradation in soil can be applied to crops that are resistant or tolerant to herbicides in order to kill weeds without attendant risk of damage to the crop.
Therefore, in order to meet the future food requirements of the world's growing population in a cost-effective and environmentally safe manner, there exists a long felt and unfulfilled need for novel target enzymes for herbicides, for new and better herbicides inhibiting such target enzymes and for plants tolerant to these new and better herbicides.